In the prior art, when a new IC card was being connected to a motherboard bus, the motherboard bus had to be deactivated, thus the bus could not be used by another IC card which had previously been connected. Deactivation was necessary because noise signals could be added to the bus by the new card during insertion, such noise signals negatively impacting the use of the bus by the existing IC cards previously inserted. For example, data being transmitted along the motherboard bus using an existing IC card could be lost during insertion of the new IC card.
Hot pluggable connections between IC cards and a motherboard have been developed in which it is not necessary to deactivate the motherboard bus during insertion of a new card. In these prior art devices, edge connectors are located on the IC cards for connection to the motherboard. When the IC card is connected to a corresponding receptacle on the motherboard, both power connections to the electrical components on the IC card and general purpose signal connections (e.g. for data and addresses) are established during the same connection. To ensure a stable operation of the bus while a card is connected, it is necessary to make sure that power and general purpose signal connections are made in a certain order. For example, it is better to have the power connections made before the general purpose signal connections.
In U.S. Pat. No. 5,210,855 to Bartol, for example, a connection sequence is described in which first ground connections are made, then power connections are made and finally general purpose signal connections are made.
However, a problem has existed in these devices. Specifically, when the power connection is made between the IC card and the motherboard bus, power is applied to the card immediately. This causes a short circuit to exist across the motherboard power bus. This can cause many problems to occur as follows. First, physical damage to the connectors can occur, for example, the connectors can be deplated by the temporary short circuit. Second, disturbances to the signal lines on the motherboard bus can be created by the short circuit on the power bus by electromagnetic interference. Third, regulated voltage levels on the motherboard bus can be caused to fall out of regulation, thus severely effecting all other IC cards connected to the motherboard bus.
Another problem which has existed in the prior art "hot-pluggable" devices mentioned above is that when a card containing active elements is physically removed from the motherboard, the active levels existing on the connectors can cause disruptions to occur to the motherboard bus.